Cal. Rev. & Tax. Code § 32401

If the board determines that any amount of tax, penalty, or interest has been paid more than once or has been erroneously or illegally collected or computed, the board shall set forth that fact in its records and certify the amount collected in excess of what was legally due and the person from whom it was collected or by whom paid, and credit the excess amount collected or paid on any amounts then due from the person from whom the excess amount was collected or by whom it was paid under this part, and the balance shall be refunded to the person, or the person’s successors, administrators, or executors. Any determination by the board pursuant to this section with respect to an amount in excess of fifty thousand dollars ($50,000) shall be available as a public record for at least 10 days after the effective date of that determination.